Harmouche-Karaki et al. Nutrition Journal (2020) 19:65 https://doi.org/10.1186/s12937-020-00581-5 RESEARCH Open Access Development and validation of a quantitative food frequency questionnaire to assess dietary intake among Lebanese adults Mireille Harmouche-Karaki1* , Maya Mahfouz1, Jawaher Obeyd1, Pascale Salameh2, Yara Mahfouz1 and Khalil Helou1 Abstract Background: The food frequency questionnaire (FFQ) is the most frequently used method to assess dietary intake in epidemiological studies evaluating diet-disease association. The objective of this study was to validate a FFQ for use among Lebanese adults by evaluating various facets of validity and reproducibility. Methods: The quantitative 164-items FFQ was validated against the average of six 24-h dietary recalls (DRs) in a sample of 238 Lebanese adults. Reproducibility of the FFQ was assessed by administering it twice within 1 month’ time interval. Results: Positive statistically significant Pearson correlations were observed in most macro and micronutrients between the FFQ and the six 24-h DRs, ranging from 0.16 to 0.65, with two thirds of the correlation coefficients exceeding 0.3. Energy, gender, and age-adjusted statistically significant Pearson correlation coefficients ranged from 0.14 to 0.64, with two thirds of the coefficients exceeding 0.2. Intakes from the FFQ were mostly higher than those of the 24-h DRs. Mean percent difference between nutrient intakes from both dietary methods decreased remarkably after using energy-adjusted mean intakes. Values were acceptable to good for all macronutrients and several micronutrients. Cross-classification analysis revealed that around 64.3 to 83.9% of participants were classified into the same and adjacent quartile whereas grossly misclassified proportions ranged from 3.7 to 12.2%. Weighted kappa values ranged from 0.02 to 0.36 with most of them exceeding 0.2. In indirect validity analysis, key nutrient mean intakes estimated from the six 24-h DRs were significantly positively associated with tertiles of food groups derived from the FFQ. Bland Altman plots showed that the majority of data points fell within the limits of agreement (LOA) for all nutrients. As for reproducibility analysis, ICC values were all statistically significant ranging from 0.645 to 0.959 and Bland Altman plots confirmed these results. Conclusions: Based on various aspects of validity and reproducibility, and an extensive range of statistical tests, the present FFQ developed for a Lebanese community is an acceptable tool for dietary assessment and is useful for evaluating diet-disease associations in future studies. Keywords: Food frequency questionnaire, Validity, Reproducibility, Macronutrients, Micronutrients, Nutrient intake, 24-h dietary recall, Nutritional epidemiology, Statistical tests, Lebanon * Correspondence: [email protected] 1Department of Nutrition, Faculty of Pharmacy, Saint Joseph University of Beirut, Lebanon B.P. 11-5076 – Riad el Solh, Beirut 1107 2180, Lebanon Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Harmouche-Karaki et al. Nutrition Journal (2020) 19:65 Page 2 of 19 Introduction and nutrients is needed in order to evaluate the associ- Several epidemiological studies investigate the effect of ation of diet with health and diseases. diet on health and non-communicable diseases such as Thus, the aim of the current study was to validate a obesity, diabetes, cancers, as well as neurological, endo- FFQ for use among Lebanese adults, by investigating crine, and immunological disorders [1]. Such studies re- various facets of validity and reproducibility. The objec- quire precise methods to evaluate long-term dietary tives of the present study were to i) determine the rela- intake in an aim to carry out an extensive dietary assess- tive validity of the developed FFQ in measuring energy ment. A universal epidemiological method for nutri- and nutrient intakes as compared to six non-consecutive tional assessment does not currently exist [2] and the 24-h DRs ii) compare the means of nutrient intakes selection of the adequate instrument depends on the across tertiles of food groups obtained by the FFQ iii) study objectives [3]. Multiple dietary instruments are evaluate the reproducibility of the FFQ. used to determine nutritional intake [2] and they are di- vided into objective and self-reported instruments [4]. Material and methods Objective methods include nutritional biomarkers [3] Study design and participants whereas self-reported dietary instruments are generally A sample of 500 participants was drawn from the uni- divided into short-term methods (24-h dietary recalls versity database covering both students and employees, (DRs) and food records) and long-term methods (Food using a stratified random cluster sampling, with a status Frequency Questionnaire, FFQ) [3]. Each dietary assess- and sex distribution proportionate to that of the univer- ment tool has specific advantages and disadvantages [5]. sity population per campus. To be included in the study, Nutritional biomarkers are the method of choice to as- the participants had to be Lebanese, aged between 18 sess micronutrient intakes [3]; however, they are rela- and 64 years, not having medical conditions or taking tively expensive and they involve respondents burden medications that affect food intake. Selected participants [6]. Twenty-four-hour DRs provide reliable quantitative received a letter by email explaining the procedure of estimates of dietary intakes with no reactivity bias; how- the study. The agreement for participation was re- ever, the results may be affected by memory and do not quested by phone, 5 days after sending the letter. Out of represent the usual dietary intake [6]. Food records - es- the 500 participants, 305 agreed to participate in the pecially weighed food records - have the advantage of study. After providing written consent, socio- being accurate without relying on memory (more accur- demographic, anthropometric, and dietary data were col- ate portion sizes with no food omission); nevertheless lected. Based on the “non-individualized method” [15], they require relatively high cooperation from partici- also called “recommended method” [16], participants pants whose motivation might decrease over time, and with high or low reported energy intake, i.e. outside the intakes can be affected by the process of regular food re- range of 500-3500 kcal/day for women and 800-4000 cording [6]. Time and economic restrictions make the kcal/day for men, were excluded from the analysis [17]. above-mentioned methods unsuitable for use in epi- This resulted in a final sample of 238 participants. demiological studies [7]. The FFQ is a simple, less inva- sive, and inexpensive tool [6, 8] that captures the usual Development of the FFQ dietary intake because it covers a longer period of time The quantitative 164-items FFQ was developed by a [9]. In fact, when evaluating the association between diet panel of nutritionists who drafted a pre-final version of and related diseases, measuring food intake over a the questionnaire that was tested on a representative period of months to years is more valuable than measur- sample of the target population, composed of 50 stu- ing the intake of few days [8]. One main disadvantage of dents from the university. The respondents completed the FFQ is the overestimation of dietary intakes. How- the FFQ during in-depth interviews where they were ever, it is the most frequently used method to assess asked about its comprehensibility and acceptability [18]. dietary intake in epidemiological studies [2] especially The final version was composed of the following 14 food when investigating diet and disease association [10]. categories, including culture-specific food items: cereals Adopting a pre-existing FFQ poses inaccuracies, as the and grains, dairy products, fruits, vegetables, legumes, original objectives might not meet the requirements of meat, fast-food, nuts and seeds, oils and fats, salty the current study, and the FFQ yields different results snacks, sweets and beverages (hot, alcoholic and non- according to different demographic groups [9]. In alcoholic). Portion size was determined according to Lebanon, previous FFQs have been validated for use food servings by the World Health Organization Eastern among children [11] and pregnant women [12]andto Mediterranean Region guide based on United States assess the intake of antioxidant